Fever and Chills: Causes, Treatment, and When to Seek Help

Having a fever with chills is usually the body's way of fighting off infection. When your immune system detects an infection, it sends chemical signals to the brain to turn up your core body temperature. in response to the reset "thermostat," your body will start to shiver to generate heat.

Chills and body aches can also occur without fever, such as with infections like COVID-19 or bacterial meningitis. This happens when a virus or bacteria acts on the part of the brain that regulates body temperature, called the hypothalamus.

This article will explain why you get fever and chills, either together or separately. You'll also learn how to treat fever and chills at home and when it is time to seek medical care.

What Causes Fever?

A fever, also known as pyrexia, is the body's natural reaction to infection. The aim of a fever is to help neutralize germs by increasing the body temperature to where they are unable to survive.

Fevers are instigated by pyrogens. These are any substance from without or outside of the body that triggers a fever. The pyrogen may be a germ itself (such as a virus) or toxins produced by a germ (such as occurs with bacteria).

Pyrogens trigger the release of inflammatory compounds called prostaglandins from tissue at the site of the infection. Prostaglandins, in turn, "tell" the hypothalamus (an almond-sized structure situated at the base of the brain) to turn up the heat.

An increased temperature isn't officially considered a fever until it is higher than 100.3 degrees Fahrenheit (F).

Why Causes Chills?

Chills are a feeling of coldness occurring during a high fever, but they can also sometimes occur on their own without a fever.

Chills occur when your core body temperature falls below what the hypothalamus says it should. They are a physiological response that causes shivering to generate heat. (This is why you shiver whenever out in very cold weather.)

Chills with fever occur when prostaglandins reset the thermostat in the hypothalamus. The increased set point causes the body temperature to rise but also makes the person feel cold until the new set point is reached.

Chills often occur at the start of an infection like the flu.

Chills Without Fever

Certain infections can cause body aches and chills without fever. These include COVID-19 and certain bacterial infections.

COVID-19

Though fever is a common symptom of COVID-19, some people report chills without fever. The cause is not clear, but the phenomenon has been noted in people with certain complications of COVID-19. This includes having long COVID and gastrointestinal symptoms of COVID. It also includes developing a nervous system complication called Guillain-Barré syndrome (GBS).

In all three cases, the immune response to the virus is not as severe. Long COVID is associated with prolonged, low-level inflammation, while GI symptoms generally indicate milder disease. For its part, GBS is an immune reaction to the virus that mainly affects nerves.

In such cases, the infection may directly or indirectly affect the hypothalamus and temporarily lower the core body temperature.

Bacterial Infections

There are certain bacterial infections that can cause chills without fever. This may be due to the pyrogens produced by the different bacteria. Unlike viruses that can independently stimulate the release of prostaglandins, it is the toxins produced by bacteria that are pyrogenic.

Bacterial infections that can cause chills without fever include:

• Bacterial meningitis: This is the potentially severe inflammation of the membrane surrounding the brain and spinal cord (called the meninges) by bacteria.
• Lyme disease: This is a tick-borne infection that affects multiple organ systems, including the skin, joints, heart, and nervous system.
• Malaria: This is a mosquito-borne infection that causes the dysregulation of body temperature, triggering chills and shivering at one moment and fever and sweat at the next.

Accompanying Symptoms

If you have a fever and chills from an infection, you may have other symptoms as well. The symptoms you have will depend on the cause of the infection and which part of the body is affected.

Some general symptoms you might have with a fever and chills include:

• Headache
• Sore throat
• Body aches and muscle pain
• Fatigue
• Congestion and/or a runny nose
• Cough
• Abdominal pain, not feeling hungry, nausea, vomiting, and/or diarrhea
  

How to Treat a Fever and Chills

If you have a fever and chills, you might want to put on more clothes or cover up with blankets to get warm. However, this will increase your body temperature, cause more discomfort, and even lead to dehydration.

If your fever is 102 degrees F or lower and you do not have any serious signs and symptoms, you do not need to see a healthcare provider for treatment. You can treat fever and chills at home by:

• Taking over-the-counter (OTC) fever-reducing medications: Tylenol (acetaminophen) or Motrin (ibuprofen) can help bring your fever down and make you more comfortable. However, they won't make you feel better immediately—they can take an hour or longer to work.
• Warming up, but not bundling up: Wrapping yourself in an extra blanket or two to keep from shivering when you have a fever is fine—just don't overdo it. Once you get comfortable, take the covers off to avoid overheating. Wear clothes that are appropriate for the weather rather than layering.
• Staying hydrated: Drinking plenty of clear liquids when you are sick with a fever is very important. Water is best, but a cup of tea can also be soothing. Avoid alcohol.
• Sponge bathing: Dabbing your skin with a washcloth that's been soaked in lukewarm water (about 70 degrees F) can help lower a fever—the evaporation of the water cools the skin and reduces body temperature. Keep in mind that using cold water can actually make a fever higher because it will trigger chills.

Fever and Chills: When to See a Healthcare Provider

Fever and chills are not dangerous on their own—they are your body's natural way of fighting off an illness. However, fever and chills can also be a sign of a more serious condition, such as meningitis.

Call your provider or seek medical attention right away if you have a fever and chills with these symptoms:

• Stiff neck
• Confusion or irritability
• Sluggishness
• A bad cough
• Shortness of breath
• Abdominal pain
• Frequent urination

You should also call your provider or seek medical attention for some fevers in babies and children, including:

• In a child younger than 3 months: A temperature of 100.3 degrees F or higher
• Children ages 3 months to 1 year: A fever of 101 degrees F or higher that lasts more than 24 hours
• In older children and adults: A fever higher than 103 degrees F that does not respond to fever-reducing medicine; a fever that does not get better within three days; or a fever that has lasted more than five days

Summary

Fever and chills are your body's normal response to an infection. The shaking or shivering of "the chills" can be uncomfortable but usually isn't serious. You can often treat fever and chills at home with rest, fluids, and over-the-counter medications to help bring a fever down.

However, if your fever is high (more than 104 degrees F), the chills are uncontrollable, you have other concerning symptoms like a stiff neck, or you don't start getting better in a few days, seek medical care.

A Word From Verywell

Fever and chills can sometimes be caused by medications or drugs, particularly antibiotics and antipsychotics. Consult with your healthcare provider to be aware of the potential side effects of your medications. Fever and chills can also be symptoms of travel-related illnesses, particularly in individuals who have recently traveled to regions where infectious diseases such as malaria or dengue fever are prevalent. You should always inform your healthcare provider about any recent travel history if you experience fever and chills, especially if accompanied by other symptoms such as body aches or fatigue.

— KASHIF J. PIRACHA, MD, MEDICAL EXPERT BOARD